Authors:

MHD equilibrium reconstruction on the Pegasus Toroidal Experiment is the
major tool used to characterize the plasma across varied operational
regimes. Reconstructions are complicated by the presence of wall currents.
Since the vacuum vessel can carry currents comparable to the plasma current
for much of the shot duration, vessel current estimates are constrained by
an array of external flux loops. The characteristics of plasmas produced by
helicity injection by plasma guns are of particular interest.
Reconstructions of these plasmas indicate that the current profile J(r) is
relatively hollow, as expected in cases where current is driven at the edge.
This gives rise to reverse magnetic shear in the core region. In contrast,
purely ohmically driven plasmas typically exhibit peaked J(r) profiles and
minimal magnetic shear in the plasma interior. In the near future, data from
a new 2D soft X-ray camera will be incorporated as a measurement of flux
surface shape which provides a constraint on the current profile.

*Work supported by the United States Department of Energy Grant DE-FG02-96ER54375

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.DPP.VP1.4